With gradual convergence of the Internet and mobile communication, an increasing quantity of people access the Internet at anytime and anywhere by using a mobile node (for example, a cell phone).
In the prior art, when a mobile node (MN) initially accesses a first network, the MN obtains a home address (HoA) allocated by a home agent (HA) in the first network to the MN. The MN communicates with a correspondent node (CN) by using the HoA. When the MN moves to a second network, the MN obtains a care-of address (CoA) allocated by the second network to the MN. Then, the MN sends the HoA and the CoA to the HA by using a binding update (BU) message; and the HA creates a binding cache entry (BCE) for the MN, and returns a binding acknowledgement (BA) message to the MN. To avoid a problem that communication between the MN and the CN is interrupted because the MN moves to the second network, when the CN sends a data packet (the data packet includes the HoA of the MN) to the MN, the data packet is routed to a link of the first network of the MN and then is intercepted by the HA. The HA transmits the data packet to the MN by means of tunnel communication (a destination address of tunnel encapsulation is the CoA of the MN). Similarly, when the MN needs to send a data packet to the CN, the MN performs tunnel encapsulation on the data packet and sends an encapsulated data packet to the HA. The HA performs tunnel decapsulation on the encapsulated data packet after receiving the data packet on which tunnel encapsulation is performed, and then forwards a decapsulated data packet to the CN.
However, in the prior art, because the HA is deployed on a proxy server or a gateway (for example, a packet data network gateway (PGW)), load of the proxy server or the gateway is relatively heavy.